Condensation is needed for high efficiency boilers and it only occurs
if the flue gas temperature is below 120deg F, so to lower the
temperature they bring in cold winter air (which obviously defeats any
heat savings) when the boiler is running extra hot in winter.
(*****the lower the stack temperature the more effictive the heat
Stack temperature is a measure
of the heat carried away by dry flue gases and the
moisture loss. It is a good indicator of boiler
efficiency. The stack temperature is the
temperature of the combustion gases (dry and
water vapor) leaving the boiler and reflects the
energy that did not transfer from the fuel to the
steam or hot water. The lower the stack
temperature, the more effective the heat
exchanger design, and the higher the
Instead of fowl words, the appropriate path is to show where my words
don't agree with the quoted statement on boiler efficiency also posted
THEY say the lower the stack temperature the more efficient the boiler:
are they lying, no.
The chimney to bring in air is the same size as the chimney to bring
out air, so if you're bringing in air that is very cold (--10degF)
....don't you think it's going to affect the stack temperature (and the
air going out....instead of hot 140deg F) ????
And don't you think bringing in cold air defeats any efficiency gain?
I guess the best way to prove it... is to remove the pipe for the air
intake and point to inside the boiler room in winter and if the air
leaving the chimney is suddenly very very hot then you got your answer
(that is if the plastic 3 inch chimney doesn't melt first).
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